1. Field of the Invention
This invention relates generally to the field of surgery and more particularly to hemostatic instruments and devices for monitoring the collection of blood from donors. The apparatus described herein is also called a "Standard Blood Ratiometer".
2. Description of the Prior Art
The problems associated with trauma to blood cells induced or caused by the blood collection process has been described by John G. Gibson et al. in his article entitled "The Influence of Extra-Cellular Factors Involved in the Collection of Blood in ACD on Maintenance of Red Cell Viability During Refrigerated Storage" (The American Journal of Clinical Pathology, August 1956, 855-). A recognition and partial solution to the problem has also been suggested in the earlier application of McCue and Bramson referred to above.
Conventional blood collection bags currently available consist of a donor blood transfer tube attached to a main collection bag in which anticoagulant is placed during manufacture. Also connected to the main collection bag by similar but separate tubing are one or more satellite bags similar in construction, but smaller than the main collection bag. These satellite bags normally contain no liquid. The satellite bags are isolated from the main bag by a tube diaphragm which is opened when use of the satellite bag is desired.
Conventional blood collecting procedures call for receiving approximately one pint of blood (450 ml) in a plastic bag containing 63-75 ml of anticoagulant. Nearly all of the conventional anticoagulants such as ACD, CPD and CPD-Adenine are stongly acidic, having a pH in the range of 4.95 to 5.63. In addition, these anticoagulants contain the complexing agent, citrate, that strips red blood cells of essential cations, e.g., Ca.sup.+2 and Mg.sup.+2. The initial exposure of blood collected into the bag containing the anticoagulant causes trauma to a high percentage of the early collected cells because of the relatively hostile environment presented by the high proportion of anticoagulant. As the proportion of blood to anticoagulant increases, this tendency diminishes, but the damaged early cells still remain within the collection bag.
If the blood were alternatively collected in a bag that was dry and the anticoagulant added subsequently, the contact of the red blood cells with the dry plastic could also cause coagulation or clotting or otherwise induce trauma to the cells.
The conventional blood collecting procedures have also been found to have an adverse effect on the stability of blood coagulation factors (particularly Factors V and VIII) in plasma and have also had an adverse effect on the preservation of platelet function. The literature ("Blood Collection: Stability of Factors V and VIII in Plasma, V. L. Kermon, et al--Experimental Hematology, Vol. 7, No. 6, 1979, pp. 68) indicates that Factors V and VIII rapidly lose the capacity to function after being withdrawn from the circulatory system. In 0.02 M Oxalate at 22.degree. C. approximately 50% of Factor V activity is lost within two hours. In citrate phosphate dextrose (CPD) 50% of Factor V activity has been reported to be lost in 48 hours at 4.degree. C.
In a separate study ("Blood Collection: Preservation of Platelet Function", D. J. Stevens, et al--Experimental Hematology, Vol. 7, No. 6, 1979, pp. 65) the loss of platelet effectiveness and function was examined with respect to the lesion of collection and storage of the blood. It was observed that platelets from blood collected into CPD by the standard technique could not be induced to release ADP, as measured by in vitro biphasic aggregation responses to exogenous ADP or epinephrine.